anlamas

$allMark = $allMark->groupBy(function ($item, $key) {
    return strtoupper(mb_substr($item->name, 0, 1));
});

@foreach($allMark as $key => $marks)
    {{ $key }}
    @for@foreach($marks as $mark)
        {{  $mark->name }}
    @endforeach
@endforeach